Ucts protection coeporation



F. 5. SMITH ELECTRIC TRANSFORMER Filed 12. 1921 8 Sheets-Sheet l INVENTOR. M 5m A TTORNE Y.

Oct. 6, 1925. 1,555,885

F. 5. SMITH ELECTRIC 'rmusr'omsaa Filed 12. 1922 8 Sheets-Sheet 2 l NV EN TOR.

A TTORNE Y.

Oct. 5, 1925. Y 1,555,855

F. 5. SMITH ELECTRI C TRANSFORMER Filed 12. 1921 8 Sheets-Sheet 4 I NV ENTOR.

MMJM- MM ATTORNEY.

Oct. 6, 1925.

F. 5. SMITH ELECTRIC TRANSFORMER 8 Sheets-Sheet" 6 Filed D60. 12. 1921 INVENTOR.

A TTORNEY.

Oct; 6, 1925. 1,555,885

F. 5. SMITH ELECTRIC rmmsr'oausn F l 12. 1921 8 Sheets-Sheet 7 INVEN TOR.

ATTORNEY.

Patented Get. 6, 1925.

UNITED STATES 1,555,835, PATENT OFFICE.

FRANKLIN s. SMITH, or PHILADELPHIA, PENNsYLvANIA, AssIGNQR'To THE PROD- UCTS PROTECTION CORPORATION, or NEW YORK, N. 'Y., 'A'c'on-PonAT oN OFIDELA- WARE.

ELECTRIC TnANsronM n.

Application filed December 12, 1921. Seria1'No. 521,777.

To all whom it may concern:

Be it known that I, FRANKLIN S. SMITH, a citizen of the United States, and a resident of Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented an Improvement in Electric Transformers, of which the following-is a specifi cation.

The general object of my invention is to improve the mechanical, thermal and electrical characteristics of electric transformers,particularly transformers in which a gas or gases are used as the insulating and cooling means. w

Other and more specific objects of the invention are to provide: an improvement in the construction of the casing in which the transformer is contained; a transformer, the losses of which may be dissipated as heat rapidly and efliciently; means for accelerating the convection currents ofthe gas or gases within the transformer casing;-a transformer in which the wires of the primary and secondary coils are notcovered with an envelope of solid dielectric, such as enamel and cotton or the equivalent, as heretofore has been the usual practice;- an improvement. in the winding of-the high voltage coil; and an improvement in the means for supporting; and insulating from each other the adjacentturns-of the coils ofa winding; Y

Other objects and advantages of my invention will be pointed out in the detailed description thereof which follows or will be apparent from such description. I

For the purpose of facilitating a clear understanding of the invention and in order that the practical advantages thereof may be more readily apparent, reference" is made to the accompanying drawings in which an embodiment thereof is shown but it will be understood that various changes may be made in the details of construction within the sc'ope'of the claims hereto appended without departing from the said invention.

In the drawings:

Fig. 1 is'a view in elevation of an electric transformer constructed in accordance with my invention;

Fig. 2 is a vertical longitudinal sectional view of the casing, taken on the line 22 of Fig. 3;

Fig. 3 is a transverse sectional view of the top dome-shaped portion of the casing,

other portionsofthe structure being shown in top plan;

Fig. i is a vertical sectional view of a portion of thecasing showing adetail of construction thereof; ,7

Fig. 5 is a transverse sectional view of the transformer-structure, the right and left hand-"portions..thereof being-taken along different. planes, the said view looking .upward from the bottom of. the transformer, certain portions ofsthe structure within the casingjbeingnshown in :bottom plan and other portions thereof in transverse section also the structure, as shown in Fig. 5, has been turned 1 through an angle. of 90, with respect to the position shown inFig); l;

'Fig. 6 is a view similar to Fig. 3, I ut with portions of the transformer structure within the casingqshown in top plan view; Fig. -7 is,;a view in side elevation of the .plug fitted within an opening in the side of the transformer casing 1 near "the bottom thereof for supporting the,v connections for supplying current to or conducting current .from;,the -low. .voltage coils of the transformerw, I

Fig-8. is a-n., irregular longitudinal sectional viewa the casingbeing shown in section along the line 8'8 of Fig. 5, while .the interior structure is shown partly in section .and partlyinv side elevation, asindicated by thedashandfdot line 8.8;

v 9 is'a longitudinal sectional view of one of the high voltage terminals;

- Fig. 10 .is a horizontal transverse sectional view taken along the linel010 of Fig7; .1. FigJll isaview in side. elevationof the means, of solid dielectric. .for supporting the high :voltage coils. of the transformer,

the outer wires of the said coils being shown also in'elevation; Fig.'12 is a transverse sectional view of theinsulating supporting means shown in Fig. 11; with one of the coils supported thereon shownin plan;

Fig. '13 is a vertical sectional view .through thesaid coils; 1

Fig. 14 is a perspective view of one of the insulating elements also employed as a spacer of adjacent coils and of turns of a coil.

Fig. is a view similar to that shownin Fig. 12 but-showing vertically arranged insulating means intermediate portions of the Fig. 16. is aviewirrelevation of aportion or section of the structure shown in Fig. 15;

Fig. 17 is a vertical sectional-view taken on the line 17-17 of Fig. 15 of a portion or section of the high voltage winding of the transformer;

Fig. 18 isa view in sideelevation of the low voltage winding or coils;

Fig. 19 is a top plan-view of the same with the insulating supporting'meanstherefor shown in section; and

Fig. 20 is a view'in side elevation of the casingof atransformer constructed inaccordance with my invention with the interior structureshown in-outline and with transformer coils conventionally shown.

Referring tothe drawings: It will" be noted that the casing comprises a cylindrical portion 1'' and a dome portion 2, the latter being o-f'less diameter than the portion 1. The bottom-end'of'the dome portion 2'extends intoan opening in the upper end of the portion 1 and is securedtheret'o by 'welding-or'otherwise so-as' to form agas'tight joint. The lower portion of the-casing 1 is closed by: means ofa shell'o; the-upper end of which-projects into the lower end'of the portion 1' of the casingand is'securedthere to'by welding; so as-to' produce a gas tight joint. The-bottom shell is placed-'iirposition andwelded to the casing after the transformer apparatus has been placed' a'nd securedtherein: The-diameter of the dome portion-2beiiig less than that of-'tlie "portion 1- of'the, casing. it follows that tliemr end portions of the latter extend in to form an annular shoulder portion! sarrounding the lower-end o'f the-portion 2'. Openings 5. are provided in the shoulder portion 4, while-- openingsfl are-providedin the upper-end part of the dome portion 2. The openings 5 and (iareequaY in number andare arranged in couples vertically. The openings of'each verticalcouple are incomrmmicatiom upon theoutside of' the dome portion 2 through thehollow U-shapedmem hers '8, the edges of 'the-sides'and' the upper and lower ends thereof being'secured to the casing, asindicated at 9; by welding' or otherwise. For the=pmpose oi strengthening-the U-shaped" members 8 I- have provided the transverseplates-10' which are-arranged longitudinally therein-and the opposite edges of which arosecured'to theopposite sidesof thesa-id" U-shaped members- For a-nu'rpose tobe hereinafter referred to, the dome portion 2 is provided' with three radially arranged inwardly extending fiansres- 14.

The core =15is"ofknown-construction comprisin g a -'plu-ral'ity of L=slrapedsteel1laminae arranged in known manner and'as indicated generally in the drawings. The four groups of these lamina: are clamped adjacent their outer sides between the opposing flanges of angle irons 16 between-which and the said laminae solid dielectric 17 is interposed. The angle-ironsare secured or clamped together by means of bolts 18 is indicated. The upper and lower end: portions of these angle irons are secured by means of bolts 19 to the outer ends of bracket-like projections 20' which extend outwardly from the ring: shaped members 21, there being one of these members adjacent the bottom portion 1 of the casing and one adjacent the top portion thereof. The projections 20 are arranged inpairs as isshown in Fig. 5. For the purpose of adjusting and tightening the respective groups of laminae constituting the core I have provided the adjustable screw threaded bolts 22 which are in screw threadedengagement with one of the projections 20 0f each pair. The inner ends of these adjustable bolts 22 contact with plates 23 as indicated" which are held or kept out of Contact with the core laminae by means of solid dieicctric 85, as show-n. The opposite side of e ch .qroupof plates rests against a sheet of solid'dielectrio 24 which is interposed hetweenthe said respective. groups and" the other one of the pairs of project ons 20.

25 d'esignates ringmembers concentrically situated with respect to-the ring members 21. The ringmembe'rs 25 are provided with four radially extending projections 26", the outerend portions o f which are bifurcated forming bifin'ea't ions 27. The bifurcations 27 are likewise provided withprojections 28 which are secured" to the ring members 21. The projections 28+ associatedwith-the lower ring members 25 extend downwardly while those associated with the upper one of the said ring memhers extend upwardly;- The projections 28} are" connected or secnred= to the ring members 2115 7 means of bolts 30.

The high -voltage winding. '32 ofthe'transformer is supported uporr vertically arranged bars 35- of" solid dielectric which liars-are arranged'inpairs'as indicated, and the'upperand' lower end's'thereof are so cured-to the inner sides of the bifurcations 27 of theproject-ions-26; It'will be noted that these bars taper from their central. portions=to thei'rmppositvendsand that in consequence the number of turns of wire ineach coil decreases from the center in opposite directions. The slots within the bars" 35 within which the turns of wire of theqre spective coils 36 are situated may be formed by" cuttingparallel transversely arranged slots in close relation to each other, as is indicated in Fig. 8 of the drawings. Instead, however; of thus forming the: slots the respective groupsof coils constituting the high voltage winding may be separated by means of alternately arranged slotted spacers of solid dielectric 37, as indicated in Figs. 12, 13 and 14. It will be noted that in these Figs. the turns of the respective coils are situated in the slots 38 of the respecive spacers 37, and that each group of turns is separated from the next adjacent upper and lower groups by the said spacers.

In the several forms of construction the wires are bare; that is, they are not encased or inclosed in a coating or envelope of solid dielectric. In the form of construction as illustrated in Figs. 12, 13 and 14, in which the wires of the high voltage windings are relatively large, insulation between turns and coils is effected entirely by the gaseous dielectric and cooling medium except the relatively smaller part of the winding partially enveloped by the spacers 37 and strips of solid dielectric 51.

In the construction shown in Figs. 15 to 17 the wires are relatively thin and in consequence it is deemed advisable to interpose, between adjacent portions of the wires of each group of coils intermediate the successive pairs of insulating bars thin sheets 41 of solid dielectric. These sheets are perforated at frequent intervals, as indicated at42, and for the purpose of supporting the sheets vertically between the adjacent turns of wire, pins 43 of solid dielectric are employed, as shown in Figs. 15 and 16.

In. the construction as shown in Figs. 15 to 17 inclusive the insulating horizontal partitions or sheets 45 are plane, as indicated, and each turn of wire in each group of coils is separated by anarrow stripof solid dielectric 46, as indicated. :1

In the high voltage winding the wire is wound within the spaces between adjacent insulating sheets upon the supporting bars 35 and when the said spaces are full or when the winding therein is completed the wire is carried from the outside inwardly to the next space, as indicated at 50 in Figs. 15 and 16. As indicated in the said figures, the transversely and angularly extending connecting portions of wire are separated from the adjacent coils by the strips 51 of solid dielectric. The ends of the high voltage winding are connected to the wires which have connection with the high voltage terminals designated as a whole by the reference'number 61.

These terminals are fully described and claimed in my co-pending application filed March 2, 1921, Serial Number 449,212, and it is not therefore deemed necessary to re peat the description here.

The low voltage winding of the transformer is situated inside of and is concentric with respect to the high voltage winding above described. The said low voltage winding 65 is illustrated in enlarged detail in Fig. 19 and comprises two wires of relatively larger cross section, as shown. The opposite ends of these wires are connected in known manner to the terminals66, the inside ends of which are shown in Fig. 7. The adjacent coils of the low voltage winding are held or maintained in spaced relation to each other by spacing strips or blocks 66' of solid dielectric situated at intervals as shown in Fig. 19. The outer edges of these spacing strips should terminate inside the outer edges of the wires so as to allow the gas as it flows upwardly to contact freely with every part of the outer portions of said wires.

The low voltage winding is supported in spacedrelation with respect to the interior portion of the transformer core upon vertically arranged insulating bars 70 which are situated intermediate the upper and lower ring member 25, as is clearly indicated in Fig. 8 of the drawings, and also partially within the right angles between the adjacent legs of the said core, as indicated in Fig. 5.

It will be noted that gas passageways are provided between the vertically arranged insulating bars 70 and the central leg of the core ofjthe transformer, also between the coils of the low voltage winding and the said leg of core, also that a vertical opening is provided as indicated at 71 at the center of the core of the transformer, and also that gas passages are provided between the exterior of the low voltage winding, the verti cal insulating bars 35, and the portions of the high voltage winding intermediate the pairs of insulating bars 35. The coils of the high voltage winding are spaced apart so that convection currents of the gaseous dielectric and cooling medium may flow between said coils.

One of the particular objects and purposes of my invention is to provide a construction in which a gaseous dielectric and cooling medium may be used efliciently and to great advantage. To this end one of the objects has been to provide means whereby an extremely vigorous and rapid circulation of the gaseous dielectric within the casing may be effected in order to bring about or produce a more rapid dissipation of the heat which may be developed in the transformer than heretofore has been practical in so far as I am aware. To accelerate the convection currents of gaseous dielectric and cooling medium. I have provided the four sheets 80 of solid dielectric as shown in Fig. 5, the opposite edges of which contact with the interior surface of the portion 1 of the casing along lines adjacent the corners or edges of four legs of the transformer core. The presence of these sheets forms passageways intermediate the same and the subtended portions of the casing and also vertical passageways interiorly of the said sheets. The upper ends of. these sheets are connected with the lower flared end of the funnel member 81 of solid dielectric, the tubular portion 82, also of solid dielectric, of which projects upwardly into the dome portion 2 of. the casing and is centered by the radial flanges 14a. The upper end of the funnel 82 terminates a distance below the upper end of the dome portion 2 in a plane substantially co-incident with the lower ends of the openings 6.

The sheets 80,. the outwardly flared portion 81 of the funnel and the tubular portion 82 are so fitted with respect to the transformer that they form a flue, the function of which is to induce a draft and thereby accelerate the convection currents, of the gaseous dielectric and cooling medium, through the various gaspa-ssages provided.

After the transformer and the sheets 80 and the funnel 82 are all in place the bottom shell 3 is placed in position, as indicated in Fig. 8 of the drawing, and is secured by welding. The inner upper end of the said shell contacts with the-lower ends of one of the flanges of each of the angle irons'16 so that the latter are supported securely in position thereby. Prior, however, to the securing of the bottom shell in. position molten leador other material of good thermal conductivity, is poured down into the spaces between the outwardly extending. flanges of the angle irons 16,- the adjacent edges of the laminae of. the four legs of the transformer and the casing. Suitable-sheets of thin solid dielectric 88 are interposed between the said lead and core laminae so as toprevent short circu-iting of the latter.

The transformer losses are dissipated as heat, by radiation, conduction,and-convection. As these three modes of heat dissipation are common to all transformers embodying a fluid cooling medium, only the means by which increased efficiencies are obtained by my invention will be further described.

The amount of heat radiated is strictly proportional to the nature and extent of the surfaces and is independent of the presence of the gaseous dielectric adjacent to the surfaces; This is not true in transformers embodying a liquid dielectric such as oil.

However, the greater part of: heat dissipation is effected by conduction and by convection currents. By conduction through the realt-ively stationary gaseous film adjacent to the transformer surfaces, thence by convection currents to the gaseous fi m adjazent to the inner surface of the casing and then by conduction through this film.

As the reater-portion of the transformer windings are bare,-thatis, not enveloped by solid dielectrie,. the thermal resistivity of the pathsthrough which. the heat must be carried by conduction, is greatly decreased. firs-heretofore explained covection currents are greatly accelerated by flue action obtained by the fi-ue'composed of elements 80, 8-1- and: 82 shown in- Fig. 8 because of heat given to gas orgases inlong passages.

The paths of these convection currents are as follows,throughthe various gas passages provided adjacent to the windings and core and: within: the lower part of the flue and upwards and through the open end of tubular portion 82 thence descending between the tubular portion ofthe funnel and the opposed inside surfaces of the'dome portions Qand other portions thereof outwardly through: theopenings 6 and'do wn through the passageways provided. by the U-shaped parts 8. The descendingflow of the gases continues through the passageways between the sheets 80=and the subtended-portions of the casing: 1, ultimately passing inwardly underenath the lower edges of the said sheets 80,-thenee again upwardly and soon continuously.

In Fig. 20 of the drawings I have shown diagrammatically and in: dotted lines the high andzlow voltage. coils,.-86 and 87, with.- in thefcasing; the connectionsth'ereof with their respective: terminals, and their relation to the meansfor e'fiectingmirculation of the. cooling medium,wliich: is thegaseous dielectric. Any suitabledielectricmay be employed but prefer to employ a. mixture of nitrogen a'nei'heliimn. However, nitrogen alone has been employed with very satisfactory results. Tliegas-isemployed'under pressure-greaterthanatmospheric and up to about fifteen-atmosphere.

Having. thus described my invention, what I claim and desire to seeu'reby'lletters Pat'- ent is;

1'. In atransfbrmerstructure; the combination: of the 'transformer,1 means: situated at intervals for supporting the high. voltage winding. thereof, the portions-of the wire of said winding-intermediatesaid supports be ing bare on all sidesandspacted from each other, whereby the cooling medium within the transformer casing impingeupon ail-parts of the -.surfaces'=0fr the said portions ofiwire, a hermetically sealed casing: for the transformer, and means associated with-the transformer and within the casing for providing passagewaysthrough which there is a continuous circulation of the cooling medium upwardly adjacent to the parts of the transformer and downwardly uponthe outside of the said transformenand within the said. casing.

52. In a transformer structure. adapted to the use of a gaseous dielectric, thecoinbination of a hermetically sealed exterior casing having a reduced upper end portion, a transformer within the lower portion of said casing, which casing extends a substantial distance above said transformer, an interior flue within which said transformer is situated which interior flue is open at its upper and lower ends, and the upper end of which is of reduced diameter and extends a substantial distance above said transformer into the reduced upper end portion of said casing, and the said interior fluebeing spaced from the interior of said exterior casing so as to form passageways between .the said casing and said flue throughwhich currents I of the said gaseous dielectric descend.

A transformer, including a high voltage winding composed of parallel coils, supports of solid dielectric. arranged at intervals for supporting said winding, the portions of wire upon said supports being separated from each other by solid dielectric, and the portions thereof intermediate said supports being bare.

4. VA transformer situated within a hermetically sealed casing containing a gaseous cooling medium which transformer includes a high voltage winding, of parallel coils, supports arranged at intervals; for supporting said .coils, the portions ofcoils, upon said supports being separatedfrom eachother by a solid dielectric material and; the portions thereof intermediate thesaidsupports being separated only by the, said gaseous coohng medium. I

5. In a transformer structure adapted to a gaseous insulating and cooling medium, the combination of a gas tight casing,; a fine within said casing, the upper and-lower ends and sides of which;-are spaced from the upper and lower ends and sides of said casing whereby a passageway is formed within said casing exteriorly of said flue,and a transformer within said flue, the windings of which are substantially bare. w

6. In a transformer structure, the combination of a hermetically sealed casing having a dome portion atits upper end, a transformer situated within the casing a distance below the said domeportion, a funnel situated above said transformer and extending into said dome portionand terminating below the top of the. latter, the diameter of the tubular portion of said funnel being less than the internal diameter of the said dome portion whereby a space is provided between the said tubularportion and the said dome portion, and a plurality of sheets connected at their upper ends to portions of the lower flared end of the said funnel, the said sheets subtending portions of the said casing to form passageways, the lower ends of which are open and the upper ends of which are in communication with the space between the exterior of the said funnel and the adjacent opposing portion of the casing.

7. In a transformer structure adapted to a gaseous cooling medium, the combination of a transformer, the wires of the windings of which are bare, a hermetically sealed casing having a dome-shaped extension at its upper end directly above the said transformer, a funnel situated above said transformer and the tubular ortion of which extends into said dome-s iaped extension, and means upon opposite sides of said transformer intermediate the same and adjacent portions of said casing co-operating with the latter to form passageways to direct the heated gases upwardly into the said funnel which gases after escaping from the upper end of said funnel descend upon the outer side thereof and through the said passageways.

- 8. In a transformer structure adapted to a-gaseous cooling medium, the combination of a transformer, a hermetically sealed casing surrounding said transformer and having a-dome-shaped portion at its upper end of less diameter than the body portion thereof, the said body portion having a plurality of openings in its top outside the lower end of saididome-shaped portion, and the said dome-shaped portion having openings inits upper end portion and also being provided with tubular membersupon its outer side, the lower end of each of which is in communication with one of the first named openings and the upper end of which is: in, communication with one of, the second named? openings whereby open-ended passageways are prpvidedon the outer side of -said, dome-shaped portion a funnel situated above the transformer and sup orted thereon, the tubular portion of sai funnel extending upwardly into the said dome-shaped portion and terminating below the upper end thereof, and the lower end of said fun- .nel being provided; with sheets which extend downward ly ,and; .terminate adjacent the -lower end of, the 'casing, the said sheets, co-

" operating with the adjacent opposing port ions.-of saidcasing to form passageways,

,the said passageways beingin open communication at their lower ends with the lower portion, of the interior of said casing and communicating at their upper ends with thespace between the funnel and the said casing and with the said passageway upon theouter side of the saiddome-shaped portion of the casin 3 b 9. In a trans ormer structure, the combination of. an exterior hermetically sealed.

casing having. a dome-shaped portion at its upper end, a transformer within the lower portion of said casing, an open-ended casing within the said exterior casing and supcommunication at their upper'endswiththe space between said portions and at their lower ends with the lower portion of the interior ofthe said'external easing.

10. In a transformer structure, the combination of a hermetically sealed exterior casing having a dome-shaped portion at its upper end, a transformer situated within and concentrically of the lower half portion of-said casing, the wires constituting the winding of said transformer being bare and 'the'respective coils and the portions of wire of each-coil being separated from each other -so asto provide spaces between the said coils-and the said wires for the free passage ofia cooling medium, an internal cas ing supported upon the said transformer and having a portion of less diameter than the interior ;'diameter of the said domeshaped-portiomwhich proj sets into the latter "and tenninates a distancebelow the top thereo-fi and alsohavingside portions which co-opena'tegwitih the portion of the said ex- 't'erioi' easing'in opposed relation to the said transfer-Inter to form passageways the lower fonds-ofwhich-communicate with the lower portions of "the I said exterior and interior 'casings',*and the 'npper'j-portions of which ,ra're-in 'communiea-tionWith the space be- "tween jthe domeshaped-portion oft-he exter'ior casing andth'e portion of the interior casing-projecting into the llatter.

l1. "In a transformer structure, thecomhin-ationof a hermetically sealed casing having a-dome portionat its upper-end of sub- 'stantia-lly {less diameter: than the ,lowerportionfa transformer situated within the said lower-portion, afunnel "having its tubular portion extended into said dome portion, the eiiter'naldiameter of said tubular portion being less thanithe interior. diameter of said deme portion, and the lower flared end-portion hf said -fu-nnel :being supportedon said jtransformer, {,and'f-sheets -c onnected to the lower end of said funnel. and-subtending the a-ng'les'between thellegs :of-the core of said transformer and also subtending portions of the said casing to form internal and external passageways I .12. A-transformer casing havinga dome shaped portion at its upper end, hollow riblike portions secured atintervalsxtothe.outer s'ideof the said dome-shaped portion, and the said dome-shaped portion having opengreases ings in its upper end in communication with the upper ends of the said rib-like portions, and the said casing having openings therethrough outside of the lower end of said dome-shaped portion which openings are in communication with the lower ends of the said hollow rib-like portions.

13. A hermetically sealed casing for electric transformers, comprising portions of different diameters the portion of smaller diameter projecting upwardly a substantial distance from the top of the portion of larger diameter, and the said smaller portion being provided with passageways exteriorly thereof, the upper ends of which communicate with the interior of the top portion thereof, and the lower ends-with the top portion of the larger portion of said casing, whereby portions of'the dielectric within the casingescape from the upper part of the smaller portion of said casing and descend through-the said passageways to the upper part of the int-eriorof the larger portion of said casing.

14. A transformer comprising high and low voltage windings situated in-spaced relation to each-other, the space between the said windings being adapted to permit the passage of a fluid cooling medium therethrough, insulating sup-ports situated at intervals for supporting the wiresof thesaid windings, the said supports comprising means for supporting the wires in each of the windings in sepa-rated relation with re spect to each other, and the said Wires being bare on all sides.

-15. A transformer, including-a hi' h voltage winding, the zwireszof said win ing being divided into-groups of coi'ls the end of --all portions-of'the surfaces of the wires i'nter nediate the said supports. 3

-16. A -'transformer including a high voltage -.wind i-ngthe wires of-whichare divided into groups of coils,- vertical insulating bars situated ati-ntervals in radiail relation to the axis of the tra-ns'ft'oI-Iner for supporting the said high-voltage-winding,;-eachof the said bars being provided with insulating means for separatingadj acent coils, and means for separating the adjacent wires 'of the respective coils, and the portions ofthe wires of the respective coils intermediate adjacent bars being'bare-onall-sides;

-17. A trans-former, including a high voltage w-indihg,t-he wires of which are-divided into groups of coils, supports of insulating material arranged at intervals for supporting the said Winding, each said support comprising two bars situated in proximity to each other and insulating means carried upon each of the said bars for supporting the Wires of adjacent coils, and the portions of Wire intermediate each support and between the bars of each support being bare, substantially as described.

In testimony that I claim the foregoing as my invention, I have hereunto signed my name this 7th day of December, A. D. 1921.

FRANKLIN S. SMITH. 

